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This invention relates to the field of computer input devices. In particular, this invention includes an apparatus, method and algorithm for the intuitive rotational control of three dimensional graphical objects displayed on a monitor.
Various computer input devices have been designed to allow user manipulation of graphical pointers, cursors or objects on a computer screen in two dimensions. Most notably, these include the common computer mouse, trackball and joystick. There are also various computer input devices that have been designed to allow for user manipulation of graphical objects in three-dimensions. However, many of the various devices designed to date are complicated to use. For example one such device is a six-degree-of-freedom (6 DoF) joystick, such as the Spaceball.(trademark)., described in U.S. Pat. No. 4,811,608 to John A. Hilton, issued (Mar. 14, 1989). However, the six degrees of freedom provided do not directly match position and orientation. The correlations of torque and force quantities to rotations and translations is reputedly difficult and unnatural to learn.
The existing devices generally involve using various buttons or wheels and require good coordination for proper use. For instance, a sequence of signals from a 2-D input device may be used to simulate a signal from a virtual 3-D trackball such as described in U.S. Pat. No. 5,019,809 to Michael Chen (May 28, 1991). The user must manipulate a virtual trackball on screen which separates the user from manipulating the intended object and tends to decrease accuracy. Other methods require awkward usage of 2-D input devices. Moreover, many of the devices are so complex, that their manufacture is uneconomical. A more intuitive device is always desirable to be more user-friendly and a more economical device is desirable as well.
A method is described in U.S. Pat. No. 5,854,623 to Edward Bullister (Dec. 29, 1998) which uses a ball whose surface is patterned with reflective Platonic solid tilings and intends to provide a more direct correspondence between rotations of the trackbar and the object. Drawbacks in this design include the need for pattern recognition algorithms and the need to introduce various additional complexities if absolute orientations are desired.
The current invention provides an intuitive, easy to use, freely manipulable computer input device for the three dimensional rotational control of a graphical object using simple, low cost materials and very simple interpretation algorithms which may be used to yield absolute measurements of orientation.
It is the object of this invention to provide an intuitive, easy to use, freely manipulable computer input device for the three dimensional rotational control of a graphical object using simple, low cost materials and very simple interpretation algorithms which may be used to yield absolute measurements of orientation. The apparatus and method includes freely rotating what can be thought of as a large trackball. Unlike an ordinary mouse-like trackball, the SO3 (special orthogonal group in 3 dimensions) device tracks rotations about all axes through the center of the ball. One of the advantages of this invention, is the very easy, intuitive control of graphical objects. There is a natural correlation between the manipulation of the device by the user and the movement of the graphical object under the control of the device. Simply put, an applications program can use the information provided by the device to rotate an object displayed on the screen the very same way that the user is rotating the ball in the device. There is no complicated coordination of buttons or simulated motion. The invention consists of hardware and the method of use of the device and software algorithms used to interpret the data read from the device. Much of the ease of operation of the device is due to the development of the proper algorithm for interpreting the signals from the input device. The current device could be useful for computer-aided design, molecular modeling, rational drug discovery, virtual reality, and educational and recreational applications which involve 3D image manipulations.